Our long-term goal is to develop immunotherapy for high-risk neuroblastoma that realizes the full potential of natural killer (NK) cells combined with antitumor monoclonal antibodies (e.g., anfi-GD2) to eradicate primary and metastatic disease. We hypothesize the following: 1) Anti-tumor efficacy of NK antibody dependent cellular cytotoxicity (ADCC) depends upon the quantity, persistence, and anti-tumor function of NK cells in tumor microenvironments. 2) Neuroblastoma cells and mononuclear phagocytes reciprocally cooperate to create a microenvironment milieu, which includes IL-6 and TGFB1, that is pro-tumor and immunosuppressive. Thus, therapeutic strategies must both maximize NK activation for ADCC and cytokine secretion (e.g., Ifni) and minimize microenvironment suppression (e.g., IL-6 and TGFB1). Our Specific Aims are as follows: 1) Identify interactions between tumor cells and mononuclear phagocytes that promote tumor growth and/or suppress anti-tumor NK functions. 2) Develop combinatorial therapy for established and minimal disease by maximizing anti-tumor activities of NK cells while abrogating pro-tumor activities of mononuclear phagocytes. Research Design and Methods. In Aim 1. we shall use our existing microarray database to gain further insight into inflammation-related gene expression of tumors from patients (e.g., IL- 6/STAT3 and TGFB pathways) and then validate findings with protein array analyses. Next, we shall use in vitro models to understand interactions between tumor cells and monocytes that increase growth of tumor cells and suppress activation of NK cells for ADCC and Ifni secretion. Finally we shall use In vivo models of local and disseminated disease in NOD/SCID mice that include bioluminescent imaging of tumor cells monocytes, and NK cells to further understand how monocytes promote tumor growth and to determine if they cause resistance to NK ADCC. In Aim 2, we shall develop combinatorial therapy that maximizes antitumor NK ADCC while negating pro-tumor and immunosuppressive contributions from tumor cells and mononuclear phagocytes. Here, we shall use In vitro models to develop strategies with drugs such as the immune modulator lenalidomide for maximizing induction of NK ADCC and cytokine secretion while modulating the pro-tumor functions of monocytes. This aim will include generating microarray data for use in connectivity mapping aimed at identifying new agents for immune modulation. The most promising strategies then will be tested with our in vivo NOD/SCID models, which include imaging, of minimal and established disseminated and local disease. These experiments will provide the basis for clinical trial development.